The invention belongs to the technical field of intelligent substation of power systems, and discloses a load power self-adaption based automatic back-up power switching system of a substation. The system comprises a substation load power and remote signaling information acquisition module, a power distribution self-adaptive load shedding module, an automatic back-up power switching module and a communication interface module, the substation load power and remote signaling information acquisition module is used for acquiring real-time load power of a main transformer and a low-voltage outgoing line of the substation and has an in-station remote signaling function, the power distribution self-adaptive load shedding module has a function of automatically judging and being self-adaptive to removal outgoing line load according to load power so as to satisfy that the main transformer is not overloaded after automatic back-up power switching, and the communication interface module is used for being communicated with a main control unit or a management background computer for information interaction and directly performing brake connecting-disconnecting control. The system can be applied to automatic back-up power switching of traditional or intelligent substations, and a convenient solution is provided for data acquisition mode diversification of the existing traditional substations or intelligent substations, and for the problem that the main transformer is prone to long-long overload operation after simple automatic back-up power switching, or essential loads lose power easily due to simplicity and current latching.